1. Field of the Invention
The present invention relates to a vehicle control apparatus that performs control in accordance with a fuel-efficient travel demand corresponding to a user operation in a vehicle having a wheel driving motor.
2. Description of the Related Art
In recent years, electric vehicles that are good for the environment such as electric automobiles, hybrid automobiles and fuel cell automobiles, have come to attention. To improve environmental friendliness, it is desirable to achieve energy saving such as improvements in fuel economy. To improve the fuel economy, it is sometimes necessary to make slight sacrifices in the operability of the vehicle or the comfort of the interior space by restricting the driving performance or air-conditioning. Since it is preferable for a user (i.e., a driver) to select an energy saving mode through a simple operation, a switch for issuing a fuel-efficient travel demand to a control unit of the vehicle may be provided. This type of switch is sometimes known as “eco mode switch” or simply “eco switch”.
For example, Japanese Patent Application Publication No. 2007-159214 (JP-A-2007-159214) describes an electric automobile having an eco switch, in which a step-up operation of a step-up converter is halted when a user turns the eco switch ON, thereby eliminating switching loss in the converter and enabling fuel-efficient travel.
However, if the step-up operation of the converter is suddenly halted when a driver turns the eco switch ON, the motor torque rapidly decreases, which causes the driver to experience an unpleasant sensation as if brakes were slammed on.
Further, although the driver depresses an accelerator to increase the speed of the vehicle during travel with the eco switch ON, the driving performance expected by the driver cannot be received because the step-up operation of the converter remains halted. Therefore, in JP-A-2007-159214, the step-up operation of the converter is resumed when an accelerator opening reaches or exceeds a predetermined threshold. However, if the step-up operation of the converter is suddenly resumed, the motor torque rapidly increases, which causes the driver to experience a strong sensation of the vehicle leaping forward.
Hence, although an improvement in fuel economy is achieved with the electric automobile described in JP-A-2007-159214 by switching the eco switch ON to halt the step-up operation of the converter, the drivability of the automobile cannot be expected when the eco switch is turned ON or when the accelerator is depressed while the eco switch is ON.